I like Unnatural Selection in this deck for the ability to turn another players creatures into Slivers, either as a combo with Sliver Overlord or, if you need to help one player take down another player, by letting his creatures take advantage of sharing the pile of Slivers abilities
PT, to receive event materials
This is optional, which means if you have some way of recurring your action cards from your discard, which emerald is very good at doing, then you dont have to take the benefit
It gains indestructible when you gain life
Mother of Runes was first printed smack dab in the middle of combo winter, with cards like Tolarian Academy, Tinker, and Memory Jar stealing a lot of the spotlight